Department of Entomology
  • About
    • At a Glance
    • Welcome From the Chair
    • Code of Conduct
    • Diversity, Equity, and Inclusion >
      • DEI Working Group
      • Resources
    • Departmental History
    • For Alumni
    • Support Entomology >
      • Steinhauer Scholarship Fund
    • Proposal Resources
    • Contact >
      • Directions
  • News
    • News
    • Seminar Blog
    • Seminar Schedule
    • Awards
  • People
    • Faculty
    • Post Docs
    • Students
    • Staff
    • Alumni
  • Academics
    • Graduate >
      • Admissions
      • MS Degree Requirements
      • PhD Degree Requirements
      • Graduate Student Resources
      • Financial Assistance
      • Award & Funding Opportunities
      • Entomology Student Organization
    • Online Masters in Applied Entomology
    • Undergraduate >
      • Entomology Minor
      • Honors Program
  • Research
    • IPM & Biological Control of Agricultural, Urban & Forest Pests
    • Ecology, Conservation, Restoration, Climate Change >
      • Pollinator Science and Apiculture
    • Evolution, Systematics and Evo-Devo
    • Genetics & Genomics and Medical Entomology
  • Extension/Outreach
    • Educational Outreach
    • Insect Camp
    • Insect Drawings
    • Insect Identification
    • Pesticide Education and Assessment Program
    • Plant Diagnostic Laboratory (PDL)

[Seminar Blog] “One should make one’s life a mosaic. Let the general design be good, the colors lively, and the materials diversified.” – Marthe Bibesco

3/15/2022

 
​written by: Eva Perry and Jonna Sanders

Dr. Joe Hanly’s research on speciation genomics in Colias Butterflies (sulphurs) of North America is the very embodiment of this phrase, through his investigation of wing patterns in the evolution and diversity of these butterflies. A post-doctoral researcher at George Washington University, Dr. Hanly’s research for the past several years has focused on understanding the relationship between genotypes to phenotypes, or rather, how specific genomes, through the processes of development and evolutionary selection, lead to specific phenotype expressions in wing patterns in Colias butterflies.
​Butterfly wings are covered in thousands of scales, each one an individual cell that differentiates during the early pupal stages of metamorphosis. Scale differentiation is controlled by specific regions of the developing butterfly’s genome, which determines pigment type and quantity in each scale based on its location on the wing. Pigment alone, however, is not enough – the structural details of the scale are an essential component to determining its color. Intricately arranged filaments of actin (a multi-functional protein) joined by ridge-like deposits of chitin create structural patterns that interact with light in different ways. This creates a remarkable amount of variation – even mirror-like reflectance1 (Figure 1).
Figure 1: Variation in the shape of butterfly scales shows how color is determined by structure1. Note that the “metallic” scale structures in the two different species are strikingly similar: wide and flat, with filled-in spaces. The reflectance of these scales is different from a mirror, in that they reflect all light frequencies while remaining very thin. This is possible because different parts of the scale are reflecting different colors of light (instead of all at once), giving the perception of a mirror.
Figure 1: Variation in the shape of butterfly scales shows how color is determined by structure1. Note that the “metallic” scale structures in the two different species are strikingly similar: wide and flat, with filled-in spaces. The reflectance of these scales is different from a mirror, in that they reflect all light frequencies while remaining very thin. This is possible because different parts of the scale are reflecting different colors of light (instead of all at once), giving the perception of a mirror.
During the seminar, Dr. Hanly described his and his colleagues’ research using CRISPR mosaic gene knock-out techniques, whereby the removal of a specific genomic region can alter the phenotypic expression of the scale patterns on butterfly wings. Hanly’s research at George Washington University focuses upon the differences between two Colias butterfly species, the common sulfur (Colias philodice) and the orange sulfur (Colias eurytheme), which phenotypically diverged due to feeding preferences between C. eurytheme in the Western USA, and C. philodice in the Eastern USA. In comparing the wing pattern variations between C. philodice and C. eurytheme species, male C. eurytheme exhibit ultraviolet reflectance compared to C. philodice males, and females of both species. This UV reflectance is the result of scale structures that have ridges with lamellae, are uniformly spaced to interact with ultraviolet wavelengths. Ultraviolet light is trapped in these structures and is reflected back, whereas other frequencies of light are not. This system is an excellent model to test the genetic basis of sexually dimorphic wing pattern variation, as C. eurytheme and C. philodice are capable of hybridizing with each other.
 
With regard to mating behaviors, the female Colias butterflies are more selective than the males2. In Colias butterflies, sexual traits such as preference, fertility, pheremone expressions, size determination, and color effects are mapped to the same sex chromosome. C. philodice selects conspecific mates based upon olfactory clues, whereas C. eurytheme selects for traits based on ultraviolet iridescence.
 
Like birds, female butterflies are heterogametic (ZW) while the males are homogametic (ZZ). For the two Colias species studied by Dr. Hanly, the only individuals that express UV reflectance on the dorsal wings are C. eurytheme males; thus the trait is assumed to be homozygous recessive. While females with a C. eurytheme Z chromosome do not express UV reflectance on their wings, they do show a preference for males that express it, suggesting that the genetic determination of mate preference is located on the same chromosome as UV reflectance3. All crosses of these two species are capable of producing offspring, but if a C. eurytheme female mates with a C. philodice male, the female offspring (an individual with a C. eurytheme W sex chromosome and a C. philodice Z sex chromosome) will be sterile. This results in strong selection pressure for females to select males that display UV reflectance.
 
To begin the process of determining which gene or genes on the sex chromosome determine UV reflectance, Dr. Hanly and his colleagues collected C. eurytheme and C. philodice butterflies from Hedgeapple Farm in Buckeystown, Maryland. They crossbred both species to obtain hybrids and sequenced the genomes, focusing on regions where both recombination and divergence were high. High recombination and high divergence indicate that selection is likely happening. Their results indicated a region of twenty different genes that could be responsible for UV reflectance, including bab (bric à brac), a gene responsible for repressing male-specific traits in the model organism Drosophila4.
 
Could bab be associated with UV reflectance in male C. eurytheme? A closer look at the genetic expression in their scale cells showed that bab is repressed in scales with UV reflectance, and expressed in scale cells without. This seemed to support their hypothesis that bab repression results in UV reflectance, so to test it, a CRISPR-facilitated knockout of bab was used on C. eurytheme males, C. philodice males, and also C. eurytheme females5. All three groups exhibited UV reflectance in wing scales when bab was fully repressed (Figure 2), which indicates it is highly likely that bab is the gene responsible for determining UV reflectance in Colias.
Figure 2: Images of UV reflectance gain as a result of bab mosaic KO in C. eurytheme and C. philodice, showing both visible and UV light images of the top (dorsal) and bottom (ventral) planes of the specimens’ wings5. Note that C. eurytheme males are only UV reflectant dorsally in the wild type.
Figure 2: Images of UV reflectance gain as a result of bab mosaic KO in C. eurytheme and C. philodice, showing both visible and UV light images of the top (dorsal) and bottom (ventral) planes of the specimens’ wings5. Note that C. eurytheme males are only UV reflectant dorsally in the wild type.
Dr. Hanly and his collaborators’ remarkable research on gene expression of butterfly wing scale iridescence clearly highlights the role of specific genes in evolutionary changes between C. philodice and C. eurytheme. These genomic markers, to which Dr. Hanly’s research elucidates, are responsible for controlling the repression of ultraviolet reflectance, and demonstrate important links between the role of iridescence in mating behaviors and speciation differences between the two groups. Future research is needed on UV reflectance as an evolutionary marker of bab, and the precise mechanism of its role in repression of UV scales in Colias butterflies.
 
Works Cited:
  1. Ren, A, et al. (2020). Convergent evolution of broadband reflectors underlies metallic coloration in butterflies. Frontiers in Ecology and Evolution 8. DOI: 10.3389/fevo.2020.00206
  2. Silberglied, RE, & Orley, RTJr. (1978). Ultraviolet reflection and its behavioral role in the courtship of the sulfur butterflies Colias eurytheme and C. philodice (Lepidoptera, Pieridae). Behavioral Ecology and Sociobiology 3: 203-243. DOI: 10.1007/BF00296311
  3. Grula, JW, & Orley, RTJr. (1980). The effect of X-chromosome inheritance on mate-selection behavior in the sulfur butterflies, Colias eurytheme and C. philodice. Evolution 34(4): 688-695. DOI: 10.1111/j.1558-5646.1980.tb04007.x
  4. Kopp, A, et al. (2000). Genetic control and evolution of sexually dimorphic characters in Drosophila. Nature 408: 553-559. DOI: 10.1038/35046017
  5. Ficarrotta, V, et al. (2022). A genetic switch for male UV iridescence in an incipient species pair of sulfur butterflies. Proceedings of the National Academy of Sciences 119(3). DOI: 10.1073/pnas.2109255118
 
Authors:
 
Eva Perry is a second year PhD student in the Burghardt Lab. Her research addresses urban plant-insect ecology, with particular interest in the interactions between environment, herbivory, and tree phytochemistry.
 
Jonna Sanders is a first year PhD student currently on rotation in the Lamp Lab. Her research interests include Hymenoptera, use of parasitoids in pest management, as well as novel approaches to crop rotation.


Comments are closed.

    Categories

    All
    Awards
    Colloquium
    Faculty Spotlight
    Fall 2013 Colloquium
    Fall 2014 Colloquium
    Fall 2015 Colloquium
    Fall 2016 Colloquium
    Featured
    Innovation
    News
    Publications
    Science Projects
    SESYNC
    Spring 2014 Colloquium
    Spring 2015 Colloquium
    Spring 2016 Colloquium
    Talks
    Undergraduate

    Archives

    September 2022
    August 2022
    July 2022
    May 2022
    April 2022
    March 2022
    February 2022
    January 2022
    December 2021
    November 2021
    October 2021
    September 2021
    August 2021
    July 2021
    June 2021
    May 2021
    April 2021
    March 2021
    February 2021
    January 2021
    December 2020
    November 2020
    October 2020
    September 2020
    August 2020
    July 2020
    June 2020
    May 2020
    April 2020
    March 2020
    February 2020
    December 2019
    November 2019
    October 2019
    September 2019
    August 2019
    July 2019
    June 2019
    May 2019
    April 2019
    March 2019
    February 2019
    January 2019
    December 2018
    November 2018
    October 2018
    September 2018
    August 2018
    July 2018
    June 2018
    May 2018
    April 2018
    March 2018
    February 2018
    December 2017
    November 2017
    October 2017
    September 2017
    June 2017
    May 2017
    April 2017
    March 2017
    February 2017
    January 2017
    December 2016
    November 2016
    October 2016
    September 2016
    August 2016
    June 2016
    May 2016
    April 2016
    March 2016
    February 2016
    January 2016
    December 2015
    November 2015
    October 2015
    September 2015
    August 2015
    July 2015
    June 2015
    May 2015
    April 2015
    March 2015
    February 2015
    January 2015
    December 2014
    November 2014
    October 2014
    September 2014
    August 2014
    June 2014
    May 2014
    April 2014
    March 2014
    February 2014
    January 2014
    December 2013
    November 2013
    October 2013
    September 2013

    RSS Feed

Picture
Picture
Picture
Department of Entomology 
University of Maryland 
4112 Plant Sciences Building 
College Park, MD 20742-4454
USA

Telephone: 301.405.3911 
Fax: 301.314.9290
Picture
Picture
Web Accessibility
  • About
    • At a Glance
    • Welcome From the Chair
    • Code of Conduct
    • Diversity, Equity, and Inclusion >
      • DEI Working Group
      • Resources
    • Departmental History
    • For Alumni
    • Support Entomology >
      • Steinhauer Scholarship Fund
    • Proposal Resources
    • Contact >
      • Directions
  • News
    • News
    • Seminar Blog
    • Seminar Schedule
    • Awards
  • People
    • Faculty
    • Post Docs
    • Students
    • Staff
    • Alumni
  • Academics
    • Graduate >
      • Admissions
      • MS Degree Requirements
      • PhD Degree Requirements
      • Graduate Student Resources
      • Financial Assistance
      • Award & Funding Opportunities
      • Entomology Student Organization
    • Online Masters in Applied Entomology
    • Undergraduate >
      • Entomology Minor
      • Honors Program
  • Research
    • IPM & Biological Control of Agricultural, Urban & Forest Pests
    • Ecology, Conservation, Restoration, Climate Change >
      • Pollinator Science and Apiculture
    • Evolution, Systematics and Evo-Devo
    • Genetics & Genomics and Medical Entomology
  • Extension/Outreach
    • Educational Outreach
    • Insect Camp
    • Insect Drawings
    • Insect Identification
    • Pesticide Education and Assessment Program
    • Plant Diagnostic Laboratory (PDL)